Update pycryptodome version to latest

PyCryptodome v3.9.7 doesn't have the required elliptic curve algorithms
to be able to support the new signed scratchpad format. This commit
updates the pycryptodome Python package version to the latest available
(v3.16.0).

Dockerfile

@@ -16,7 +16,7 @@ RUN apt-get update \
     && rm -fr /var/libapt/lists/*
 
 # Install pycryptodome package needed for scratchpad image generation
-RUN pip3 install pycryptodome==3.9.7
+RUN pip3 install pycryptodome==3.16.0
 
 WORKDIR /home/${user}